Synthetic Strategy for Construction of Highly Congested Tetracyclic Core (6-5-7-4) of Harziane Diterpenoids

The structurally intriguing tetracyclic core of complex harziane diterpenoid was constructed in 14 steps from commercially available 3-ethoxycyclohex-2-en-1-one. The key steps were a Mn/Cu-mediated oxidative 1,3-dicarbonyl radical cascade cyclization reaction, which diastereoselectively formed the core of dimethylbicyclo[3.2.1]octane structure, and a Au-catalyzed diastereoselective formal [2 + 2] cycloaddition for construction of the harziane diterpenoid tetracyclic framework. The developed method paves the way for achieving total synthesis of this type of complex natural product.

Automated summary

The structurally intriguing tetracyclic core of complex harziane diterpenoid was successfully constructed in 14 steps from commercially available compound. Key methods used include Mn/Cu-mediated oxidative 1,3-dicarbonyl radical cascade cyclization reaction and Au-catalyzed diastereoselective formal [2 + 2] cycloaddition.